Browsing by Author "Wang, Jiangfan"

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Concurrent intersection point of magnetization and magnetoconductivity curves in strongly fluctuating superconductors
(2017-12-20)
Chi, Cheng
;
Jiang, Xujiang
;
Wang, Jiangfan
;
Li, Dingping
;
Rosenstein, Baruch
The thermal fluctuations contribution to magnetization and magnetoconductivity of type-II layered superconductors is calculated in the framework of the Lawrence-Doniach model. For numerous high-temperature cuprate superconductors, it was discovered that the magnetization dependence on temperature in a wide range of fields exhibits an intersection point at a temperature slightly below Tc. We notice a similar intersection point of the magnetoconductivity curves at the approximate same temperature. The phenomenon is explained by strong (non-Gaussian) thermal fluctuations with interactions treated using a self-consistent theory. All higher Landau levels should be included. Dimensionality of the fluctuations is defined, and the two- to three-dimensional crossover is the key for the existence of intersection points.
Quantum phase transition in a two-dimensional Kondo-Heisenberg model: A dynamical Schwinger-boson large-N approach
(2020-09-15)
Wang, Jiangfan
;
Chang, Yung-Yeh
;
Mou, Chung-Yu
;
Kirchner, Stefan
;
Chung, Chung-Hou
We generalize the dynamical large-N multichannel Schwinger-boson approach to study the quantum phase transition of a two-dimensional Kondo-Heisenberg model, relevant for heavy electron systems, close to an antiferromagnetic Kondo destruction quantum critical point. By breaking up a Kondo singlet into a charge fermion (holon) and a bosonic spinon, we identify and characterize the quantum phase transition from an antiferromagnetically ordered state to a Kondo-dominated paramagnetic state, and attribute a jump in the holon phase shift to Kondo breakdown. We calculate transport and thermodynamic quantities. The global finite-temperature phase diagram and the critical behavior of various physical observables therein show a close resemblance to experimental observations.